In the prior art, it has been common to provide child resistant closures which include as a feature some construction for preventing or resisting rotation between the closure and at the same time maintaining a seal to prevent leakage of contents during the initial unthreading of the closure from the container. Thus, U.S. Pat. No. 3,971,487 discloses the concept of an internal annular bead on the closure engaging a complementary bead on the finish of the container so that when the closure is initially rotated, the base of the closure is maintained in sealing contact with the finish even though the threads have begun to lose contact. In such a construction, the use of a solid closure bead in connection with the solid bead on the container has a problem requiring of high torque for application and removal. In addition, due to normal dimensional tolerances in an axial direction, the seal is not maintained when the closure is fully applied. Such closures utilize a depressable tab that engages a projection on a container so that when the tab is depressed, the closure can be rotated to remove the closure from the container.
Certain containers especially those for anti-freeze are sealed with closure that have an aluminum foil disk induction sealed over the mouth of the finish During the process of activating the induction seal, the closure may become loose and is usually retightened before the containers are shipped while the induction seal prevents leakage it is undesirable to have loose closures, especially child resistant closures.
Further, one piece child resistant closures having a tab on the closure and an abutment on the finish usually have a space between them such that the closure can be moved several degrees of rotation in the unscrewing direction before the tab contacts the abutment. When this occurs, the closure is free to move vertically with respect to the finish because the top of the closure threads are not in contact with the bottom of the container threads
Among the objectives of the present invention are to provide a child resistant closure which will maintain the oriented position with respect to the container when the closure is applied; which will resist inadvertent rotation as by vibration and thereby maintain a seal except when sufficient force is supplied to rotate the closure; which prevents the closure from moving out of sealing position when the closure is being unthreaded until the threads elevate the closure out of sealing position; which functions over a greater range of tolerances; which requires minimal torque to apply; which does not require excessive torque to remove; which closure can be utilized in connection with conventional containers having a projection and incorporating a tab with the closure for engaging the projection upon rotation of the closure beyond a certain point unless the tab is depressed; which closure can also be utilized on a container which does not require a tab; which will effectively deter and resist rotation without the necessity of close tolerances between the closure and the container; and which provides a secondary seal at the apex of an annular bead on the container; and which can be used without a tab as a conventional threaded closure having a secondary seal.
In accordance with the invention, the child resistant closure is adapted to be used with a container to provide a child resistant package and comprises a closure having a base wall and a peripheral skirt with internal threads adapted to engage complementary threads on the container. The closure is provided with a plurality of circumferentially spaced flexible fins which frictionally engage the apex only of an annular bead on the container to provide resistance to closure back off in order to resist unthreading of the closure from the container. The closure is provided with a tab which is engageable with a projection on the container to prevent unthreading of the closure except when the tab is depressed. In another form, a cylindrical surface on the skirt frictionally engages solely the apex of the annular bead on the container. The cylindrical surface may be a continuous surface or a series of closely spaced annular serrations and alternating fine grooves. The closure may also be used without a tab to provide a secondary seal on a conventional threaded closure.